An optical time-domain reflectometer (OTDR) is an important device for locating a failure point of an optical fiber link in a passive optical network (PON), and the OTDR includes an optical transmitter and an optical receiver. The optical transmitter is configured to transmit an optical detection signal, where when the optical detection signal encounters an obstacle point in an optical fiber line, Fresnel reflection occurs. The optical receiver is configured to receive a Fresnel reflection signal and determine failures such as disconnection and poor connection of a link according to the size of the Fresnel reflection signal, so as to determine responsibility of a failure and exclude the failure conveniently.
An optical transceiver is a core component for transmitting and receiving a signal in a PON network. The optical transceiver is specifically classified into an optical line terminal (OLT) used in a central office end, an optical network unit (ONU), an optical network terminal (ONT), and so on. The optical transceiver is formed by a bi-direction optical sub-assembly (BOSA) and a peripheral circuit.
Since an independent OTDR device is expensive and has large volume, it is inconvenient to detect an optical transceiver such as an OLT, an ONU or an ONT in a PON network in real time.
As shown in FIG. 1, in a conventional optical transceiver A with a built-in OTDR, a partially transmitting and partially reflecting optical filter or a fused biconical taper coupler 2a is placed out of a single-fiber bi-directional BOSA 1a. A low-speed detection signal of the OTDR and a high-frequency communication signal of the BOSA are loaded together on a BOSA laser 11a inside the BOSA 1a and are output through an output end of the optical filter or the coupler 2a. A Fresnel reflection signal returned due to occurrence of Fresnel reflection when the low-speed detection signal of the OTDR encounters an obstacle in an optical fiber, after passing through the optical filter or the coupler, is received by an OTDR receiver 3a. A received high-frequency communication signal sent by another BOSA, after passing through the optical filter or the coupler 2a, is received by a BOSA receiver 12a inside the BOSA 1a. Reliability of an optical transceiver that adopts a partially transmitting and partially reflecting optical filter is relatively low, and the volume of a fused biconical taper coupler is relatively large. Therefore, a layout of a peripheral circuit 16 of a BOSA 1a in an optical module is tight, and encapsulation is difficult.